The passenger compartment of the SEAT Leon remained stable in the frontal offset test.  Dummy readings indicated good protection of the knees and femurs of both the driver and the front seat passenger. SEAT showed that a similar level of protection would be provided to occupants of different sizes and to those sitting in different positions.  Protection of the driver’s chest was rated as marginal, based on dummy readings of compression.  Analysis of the deceleration of the impact trolley during the test, and analysis of the deformable barrier after the test, revealed that the SEAT Leon would be a benign impact partner in a frontal collision.  In the full-width rigid barrier impact, chest protection of the rear passenger was marginal but protection was otherwise good or adequate.  In the side barrier test, the Seat LEON provided good or adequate protection to all critical body areas.  In the more severe side pole impact, chest protection was rated as weak, based on rib compressions.  Control of excursion (the extent to which a body is thrown to the other side of the vehicle when it is hit from the far side) was found to be adequate  The SEAT Leon does not have a countermeasure to mitigate against occupant-to-occupant injuries in such impacts.  Tests on the front seats and head restraints demonstrated good protection against whiplash injuries in the event of a rear-end collision.  A geometric analysis of the rear seats also indicated good whiplash protection.  The car has an advanced eCall system which alerts the emergency services in the event of a crash, and a system to prevent secondary impacts after the car has been in a collision.  SEAT demonstrated that the doors and windows would be openable to allow occupants to escape in the event of vehicle submergence.

In the frontal offset test protection of the 6 year dummy was good for all critical body areas and good or adequate for the 10 year dummy.  In the side barrier impact protection of all critical parts of the body was good for both the 6 and 10 year dummies.  The front passenger airbag can be disabled to allow a rearward-facing child restraint to be used in that seating position.  Clear information is provided to the driver regarding the status of the airbag and the system was rewarded.  The SEAT Leon is equipped with an indirect 'child presence detection' system, which issues a warning when it recognises that a child or infant may have been left in the car.  Indirect systems are no longer rewarded by Euro NCAP. All of the child restraint types for which the SEAT Leon is designed could be properly installed and accommodated in the car.

Protection of the head of a struck pedestrian or cyclist was largely good, with poor results recorded on the stiff windscreen pillars and at the base of the screen.  Protection of the pelvis was good at all test locations. Protection of the femur was also good while that of the knee and tibia was good or adequate at all test locations.  The autonomous emergency braking system of the SEAT Leon responds to vulnerable road users such as pedestrians and cyclists, as well as to other vehicles.  In tests of its response to pedestrians, the system performed adequately but does not detect those to the rear of the car.  The system performed well in tests of its reaction to cyclists.  Protection against ‘dooring’, where a door is opened into the path of a cyclist approaching from behind, is available as an option but is not included in this assessment.  The system’s response to motorcyclists was good.

Overall, the performance of the autonomous emergency braking (AEB) system was good in tests of its reaction to other vehicles.  A seatbelt reminder system is fitted as standard to the front and rear seats.  The car has an indirect driver status monitoring system as standard, detecting driver fatigue but not distraction.  The lane support system gently corrects the vehicle’s path if it is drifting out of lane and also intervenes in some more critical situations.  The speed assistance system identifies the local speed limit.  The driver can choose to allow the limiter to be set automatically by the system.